WASHINGTON, Feb 18 (Reuters) - A Raytheon Co systembuilt into big blimp-like balloons has demonstrated capabilitiesthat could make it easier to detect and track certain enemyballistic missiles, the company and the U.S. Army's manager ofthe program said.

System tests in December at White Sands Missile Range, NewMexico, successfully tracked four targets mimicking tacticalballistic missiles in "high-threat" regions, Raytheon is set toannounce on Tuesday.

The hardware is known as Joint Land Attack Cruise MissileDefense Elevated Netted Sensor System, or JLENS. It includes atargeting radar and a wide-area surveillance radar with a360-degree look-around capability that can reach out to 340miles (550 km).

Each radar system flies as high as 10,000 feet with aseparate, 74-meter-long aerostat capable of operating aloft forup to 30 days while tethered to mobile moorings.

The bulbous, blimp-like aerostats work in pairs officiallyestimated to cost about $450 million - though Raytheon has saidit can lop a third off of that price.

The missiles were tracked during their so-called boostphase, it said, including two that were "ripple-fired" one afterthe other.

JLENS' "proven capabilities" provide another tool that couldhelp protect U.S. and partner forces from "the growing ballisticmissile threat" and other threats, Dean Barten, who manages theprogram for the Army, said in the release. Barten's statementwas confirmed to Reuters by an Army spokesman.

The army is preparing one of its two existing JLENS systems,formally known as an orbit, for a three-year exercise that willtie it into a high-tech shield designed to protect theWashington D.C. area from air attack.

The second existing JLENS system could be sent overseassooner. The system is designed to provide more time to detectand react to cruise missiles, manned and unmanned aircraft andother threats, compared with ground-based radar.

It also has been demonstrated to be capable of picking outmoving vehicles that could be used for attacks, including boats,cars and trucks, according to the Army and to Raytheon.

"We think JLENS is ready for action wherever it may beneeded," Mark Rose, Raytheon's JLENS program director, said in atelephone interview.

The program has been scaled back sharply by the governmentamid Pentagon belt-tightening to help paretrillion-dollar-a-year U.S. deficits.